Why do fancy-shape lab diamonds not get a cut grade?

ZKZ Editorial TeamMain answer · Product & gemmology desk

Cut grades are only well established for round brilliants. GIA says that an internationally accepted system for visually evaluating the appearance of fancy-cut diamonds does not exist at this time, and it provides a cut grade only for standard round brilliants. For an oval, pear or emerald cut, you judge the cut by looking, by measurements and by a seller's description. Other laboratories may report differently, so read the report.

What GIA says

Fact GIA says that it provides a cut quality grade only for standard round brilliant diamonds in the D-to-Z colour range, based on the stone's proportions, polish and symmetry, and that it considers brightness, fire, scintillation, weight ratio and durability in that assessment.

Fact In an FAQ, GIA also says that an internationally accepted system for visually evaluating the appearance of fancy-cut diamonds does not exist, and that research is underway to develop one. The page may predate recent work, so check GIA's current information.

Fact For laboratory-grown diamonds, GIA's updated services launched on October 1, 2025, classify each stone as Premium or Standard, and Premium requires an Excellent cut for rounds, along with other criteria. There is no equivalent cut requirement stated for fancy shapes.

Uncertain We have not verified how other laboratories report the cut of fancy shapes, and some may give grades or comments. Read each report and ask the seller what it covers.

Why fancy shapes are harder

Our advice Rounds have a standard design that has been studied for a long time. Fancy shapes such as ovals, pears and marquises vary in length-to-width ratio, outline and facet pattern, so there is no single ideal that applies to all.

How to judge a fancy-shape cut

1. See it in person. Look at the stone in daylight and indoor light. Check for dark or washed-out areas.
2. Look at the "bow-tie". Some elongated shapes show a darker band across the middle. Some bow-tie is normal, and a strong one can look dull.
3. Check the outline. Is it symmetrical and pleasing, with even curves and points?
4. Check the ratio. Length to width ratio is a matter of taste. Ask for the measurements.
5. Check polish and symmetry, if the report gives them.
6. Compare stones. Look at several stones of the same shape side by side, or ask for a video.

For the listing

Our advice Describe a fancy shape with its measurements, ratio, polish and symmetry if known, and avoid claiming a cut grade that the report does not give.

It depends Many people choose a fancy shape for its look and size, and not for a cut grade. A stone that you love in daylight is a good sign.

Related reading: Fancy Shape Lab Diamonds: Value and Design Options · Lab Grown Diamond Certification: IGI, GIA and What to Check

Sources

• GIA, How GIA grades a diamond
• GIA, Fancy-shape diamond grading FAQ
• GIA, Updated laboratory-grown diamond services (launched October 1, 2025)

Fact = stated by the cited source. Our advice = editorial recommendation. Uncertain / it depends = limits of what can be said in general.